#include <bits/stdc++.h>
#include <string>
#include <stack>

using namespace std;

struct Stack
{
    // 列表
    int *list; // [11]
    // 容量
    int capacity;
    // 栈的当前大小
    int size;
};

/** 初始化一个栈 */
struct Stack init(struct Stack s, int capacity)
{
    s.capacity = capacity;
    s.size = 0;
    s.list = (int *)malloc(sizeof(int) * capacity);
    return s;
}

/** 压栈 */
struct Stack push_back(struct Stack s, int val)
{
    if (s.size == s.capacity)
        return s;
    s.list[s.size] = val;
    s.size++;
    return s;
}

/** 弹出栈s的顶部元素 */
struct Stack pop(struct Stack s)
{
    if (s.size == 0)
        return s;
    s.size--;
    return s;
}

/** 返回栈顶元素 */
int top(struct Stack s)
{
    return s.list[s.size];
}

int main()
{

    // struct Stack s;
    // s = init(s,10);
    // s  = push_back(s,11);

    return 0;
}
